This invention relates to rubbery copolymers of ethylene, 1-butene and polyenes having specified characteristics and superior improved properties, and to a process for production thereof.
Specifically, this invention relates to ethylene-rich rubbery copolymers which are sulfur-curable and pelletizable without forming agglomerated masses, and which exhibit superior strength characteristics, especially high tensile strength at break, as well as a fast rate of vulcanization, superior moldability, improved surface characteristics, etc., and to a process for production thereof.
More specifically, this invention relates to a rubbery copolymer of ethylene, 1-butene and a polyene, characterized by having
(A) an ethylene/1-butene mole ratio of from 86/14 to 95/5, PA1 (B) an iodine value of from 2 to 40, PA1 (C) an intrinsic viscosity [.eta.], measured in decalin at 135.degree. C., of from 0.8 to 4 dl/g, and PA1 (D) a weight average molecoular weight/number average molecular weight ratio (Mw/Mn) of less than 3. PA1 (A) It has an ethylene/1-butene mole ratio of from 86/14 to 95/5, preferably from 87/13 to 94/6. PA1 (B) It has an iodine value of from 2 to 40, preferably from 4 to 30. PA1 (C) It has an intrinsic viscosity [.eta.], measured in decalin at 135.degree. C. in accordance with ASTM D-1601-78, D-2857-70, of from 0.8 to 4 dl/g, preferably from 0.8 to 3 dl/g. PA1 (D) It has an Mw/Mn ratio of less than 3, preferably from 2 to 2.9. PA1 (E) The ratio of the intrinsic viscosity [.eta.] of the rubbery copolymer to the intrinsic viscosity of a linear ethylene/1-butene random copolymer having an ethylene content of 90 mole % and the same weight average molecular weight (determined by a light scattering method) as the rubbery copolymer of the invention (g.sub..eta. *=[.eta.]/[.eta.].sub.l) is from 0.2 to 0.9, preferably from 0.3to 0.8. PA1 (a) The sample is taken into an Erlenmeyer flask together with o-dichlorobenzene so as to provide a 0.04% solution. PA1 (b) Into the Erlenmeyer flask containing the sample is added 0.1% by weight, based on the polymer solution, of 2,6-di-tert.-butyl-p-cresol as an anti-oxidant. PA1 (c) The Erlenmeyer is heated to 140.degree. C., and the contents are stirred for about 30 minutes to dissolve the polymer and the antioxidant. PA1 (d) Then, at 135.degree. to 140.degree. C., the solution is filtered by a 1 Mill:Pore filter. PA1 (e) The filtrate is subjected to gel permeation chromatography. PA1 (a) Device: Model 200, made by Waters Company PA1 (b) Column: S-type (mix type) made by Toyo Soda Mfg. Co., Ltd. PA1 (c) Amount of the sample: 2 ml PA1 (d) Temperature: 135.degree. C. PA1 (e) Flow rate: 1 ml/min. PA1 (f) Total theoretical stages of the column: 2.times.10.sup.4 to 4.times.10.sup.4 (measured with acetone) g*.sub..eta. PA1 (a) vanadium compounds expressed by the formula EQU VO(OR).sub.n X.sub.3-n PA1 wherein R represents a hydrocarbon group, X represents a halogen atom, and n is a positive number within the range of O&lt;n.ltoreq.3, and PA1 (b) organoaluminum compounds of the formula EQU R.sub.m 'AlX.sub.3-m ' PA1 wherein R' represents a hydrocarbon group, X' represents a halogen atom, and m is a positive number within the range of 1&lt;m&lt;1.5, the Al/V mole ratio in the catalyst being at least 5. PA1 O.ltoreq.X+Y.ltoreq.300 and O.ltoreq.X.ltoreq.75, preferably O.ltoreq.X+Y.ltoreq.250, and O.ltoreq.X.ltoreq.50.
Many suggestions have been made in the past about the production of rubbers of the olefinic copolymer type such as an ethylene/propylene type or an ethylene/1-butene type. It has been difficult however to provide rubbers of the olefinic copolymer type which are sulfur-curable and pelletizable without forming agglomerated masses, and which exhibit superior strength characteristics as well as other satisfactory properties such as a high rate of vulcanization, good moldability and good surface characteristics.
British Pat. No 856,737 discloses a rubbery ethylene/1-butene copolymer which is obtained by using a catalyst composed of a titanium or vanadium compound, preferably titanium or vanadium tetrachloride and vanadium oxychloride, and an aluminum alkyl compound excluding aluminum monoalkyl dihalides, such as an aluminum trialkyl or aluminum dialkyl halide, particularly trihexyl aluminum or triisobutyl aluminum. However, the British Patent is quite silent on the use of a polyene which is one essential ingredient of the rubbery copolymer of the present invention. The copolymer obtained by the British Patent is not sulfur-curable and has poor strength characteristics. This copolymer is difficult to pelletize because of too broad distributions of its composition and molecular weight, or the resulting pellets tend to be agglomerated. Furthermore, the vanadium component and the organoaluminum component of the catalyst used in the British Patent do not come within the vanadium and organoaluminum components of the catalyst specified in the present application.
U.S. Pat. No. 3,645,992 (corresponding to Japanese Patent Publication No. 21212/71 discloses a process for continuously producing a homogeneous random partially crystalline copolymer of ethylene and a .alpha.-olefin such as 1-butene, 1-hexene or 1-octene having a narrow molecular weight distribution using a catalyst which may overlay the catalyst used in the present invention. The U.S. Patent, however, does not at all describe the use of polyenes. Hence, the resulting copolymer is not sulfur-curable. To obtain a copolymer having good uniformity, it is necessary to reduce the concentration of the catalyst, and to decrease the yield of the copolymer per unit amount of solvent.
British Pat. No. 1,014,874 (corresponding to Japanese Patent Publication No. 16148/65) discloses a process for producing a sulfur-curable copolymer rubber of ethylene, an .alpha.-olefin such as propylene or 1-butene and dicyclopentadiene and/or methylcyclopentadiene dimer using a catalyst comprising an alkyl aluminum halide and a vanadium compound selected from the group consisting of VCl.sub.4 and VOCl.sub.3. The vanadium compounds as an essential catalyst ingredient in this British Patent do not come within the vanadium compounds specified in the present invention. As will be shown later by a comparative working example, the objects of this invention cannot be achieved by the use of the vanadium compounds disclosed in the British Patent.
Japanese Patent Publication No. 14542/74 discloses a process for producing an ethylene/.alpha.-olefin copolymer using a catalyst system prepared by bubbling an inert gas into the reaction mixture of an alcohol and vanadium oxytrichloride in an inert solvent, and mixing the product with an alkyl aluminum compound. This Japanese Patent Publication states that the aforesaid catalyst system should be used because the use of a vanadium compound having an alkoxy group such as VO(OR.sub.3), VO(OR).sub.2 and VO(OR)X.sub.2 in which R represents an alkyl group and X represents a halogen atom is very expensive. The Japanese Patent Publication also teaches the use of trialkyl aluminums, dialkyl aluminum monohalides, monoalkyl aluminum dihalides and alkyl aluminum sesquihalides, preferably dialkyl aluminum monohalides and alkylaluminum sesquihalides, as the alkyl aluminum compounds. The Japanese Patent Publication exemplifies propylene and 1-butene as the .alpha.-olefin and indicates the use of a polyene as an optional comonomer component. The Japanese Patent Publication specifically discloses only a rubbery copolymer of ethylene, propylene and dicyclopentadiene, and gives a specific example only of the copolymer having an ethylene content of 48 to 53% by weight. This copolymer does not have satisfactory pelletizability, and even when it is forcibly pelletized, the resulting pellets will be rapidly aglomerated and lose the shape of pellet. Of course, such a copolymer cannot have the improved properties of the copolymer of this invention which are described hereinabove.
Japanese Patent Publication No. 2924/68 discloses a process for the production of a similar copolymer to the above cited Japanese Patent Publication No. 14542/74 using a catalyst comprising the reaction mixture of an alcohol and vanadium oxytrichloride and a dialkylaluminum monohalide or alkylaluminum sesquihalide. This Japanese Patent Publication specifically shows only a rubbery ethylene/propylene copolymer, and the copolymers obtained in all of the specific working examples in this Publication have an ethylene content of 32 to 58% by weight. Such copolymers do not show satisfactory pelletizability, nor the improved properties of the rubbery copolymers of this invention.
U.S. Pat. No. 3,674,755 (corresponding to Japanese Patent Publication No. 47591/72) discloses a method for preparing an olefinic hydrocarbon copolymer which oomprises contacting ethylene and an .alpha.-olefin having 3 to 20 carbon atoms, with or without a polyene compound, with (A) a vanadium compound having the general formula VO(OR).sub.m X.sub.3-m, in which R is a radical containing cycloaliphatic hydrocarbon having 5 to 20 carbon atoms, X is a halogen atom and m is an integer from 1 to 3 and (B) organoaluminum compound having the general formula AlR.sub.n 'X.sub.3-n ' in which R' is a hydrocarbon radical having 1 to 20 carbon atoms, X' is a halogen atom and n is an integer of from 1 to 3, the concentration of (A) in the reaction medium being from 10.sup.-4 millimole per liter to 50 millimole per liter, and the molar ratio of (B) to (A) being from 1;1 to 10,000:1. All of the Examples in this U.S. Patent disclose only an ethylene/propylene rubber with an ethylene content of from 49.3 to 78.5% by mole. Such a copolymer does not have satisfactory pelletizability, nor the improved properties of the rubbery copolymer of this invention.